Cavitation reactor comprising pulse valve and resonance chamber

ABSTRACT

A cavitation reactor having a pulse valve for receiving an input fluid flow and generating a pulsed output flow that is provided to the input of a resonance chamber, such as a tube. The pulse valve uses a shaft with a number of regularly spaced lands to form fluid conduits between an input port and the output port connected to the resonance tube to cause fluid communication between the input and output ports to be regularly opened and closed, thereby producing a pulsed output that drives the formation of resonance waves in the resonance chamber. The shaft is rotated at a suitable frequency to produce cavitation bubbles that collapse in the resonance chamber without damaging the valve shaft.

PRIORITY CLAIM

This application claims benefit from International Application No.PCT/CA2014/000783, filed Oct. 31, 2014, which in turn claims priority toU.S. Provisional Patent Application having Ser. No. 61/900,539, filed onNov. 6, 2013 and U.S. Provisional Patent Application having Ser. No.61/898,833, filed Nov. 1, 2013, all of which are incorporated herein byreference in their entireties.

FIELD OF THE INVENTION

The present invention relates generally to liquid treatment systems andmethods for removal of unwanted material from the liquid, such as water,and for creating emulsions and suspensions.

BACKGROUND OF THE INVENTION

It is well known that the cavitation in fluids may have usefulapplications, such as facilitating cell lysis and facilitating thebreakdown and flocculation of contaminant particles in fluid so that thecontaminants may be separated from the fluid by precipitation of theresulting flocs. However, it has proven difficult to produce acavitation reactor that can produce cavitation on a commercially usefulscale in which the metal components of the reactor are not rapidlydamaged and rendered inoperable by the violently collapsing cavitationbubbles.

Cavitation reactors not subject to the above problems would beparticularly useful for treating effluents to remove the waste matter inthe form of sedimented sludge to recover clean water, and also forprocessing biomass for purposes of hydrolysis.

SUMMARY OF THE INVENTION

The invention provides a cavitation reactor comprising a pulse valve anda resonance chamber. The pulse valve has a housing and a valve shaft.The housing has a cylindrical bore extending laterally along the axis ofthe bore, the cylindrical bore being defined by an inner cylindricalsurface of the housing. The housing has an input port and a pulse valveoutput port. Each port provides a separate fluid communication pathbetween an outer surface of the housing and the bore. The bore may havea radius of between 1.0 inches (25.4 mm) and 2.0 inches (50.8 mm), ormay have a radius of about 1.5 inches (38.1 mm).

The valve shaft is coaxially positioned in the bore and has a centralportion and at least two lands extending radially from the centralportion. Each land has a surface and an end proximate to the cylindricalinner surface of the housing. The central portion also has a surface.The valve shaft is rotatable inside the bore around the bore axis. Thevalve shaft may be rotatable at a rate of between 90 and 200 revolutionsper second.

The lands extend laterally, along the bore axis, so that the surfaces ofthe valve shaft, in combination with the housing, define one or morefluid conduits. Each fluid conduit has a bottom portion defined by thesurfaces of two adjacent lands and the surface of the central portionextending between the two adjacent lands.

The valve shaft is continuously rotatable so that each fluid conduitrepeatedly moves between a position in which the input port and thepulse valve output port are not in fluid communication with each other,so that the fluid communication path is closed, to an open position inwhich the input port and the pulse valve output port are in fluidcommunication with each other, so that the fluid communication path isopen and fluid flows from the input port, through the conduit and outthe pulse valve output port.

The resonance chamber has a fundamental frequency and the resonancechamber is in fluid communication with the pulse valve output port. Theresonance chamber has a resonance chamber output port. The resonancechamber may be a tube, which has proximal and distal ends with theproximal end adjacent to and in fluid communication with the pulse valveoutput port. The open distal end of the tube is the resonance chamberoutput port. The tube may be substantially straight and be positioned sothat the distal end of the tube is higher than the pulse valve outputport.

Continuously rotating the valve shaft results in repeated opening andclosing of the fluid communication path so that when fluid is injectedinto the input port, a pulsed fluid flow is produced at the pulse valveoutput port, which drives a resonant wave in the resonance chamber, andthe fluid moves through the resonance chamber from the pulse valveoutput port to the resonance chamber output port.

The valve shaft may have a rear disk-shaped plate perpendicular to thebore axis. The rear plate may have a cylindrical outer surface, and besized so the outer surface of the rear plate is proximate to thecylindrical inner surface of the housing. As a result, fluid cannot passbetween the rear plate and the inner surface of the housing. The rearplate may partly define some or all of the fluid conduits.

The valve shaft may have a front disk-shaped plate perpendicular to thebore axis. The front plate may have a cylindrical outer surface, and besized so the outer surface of the front plate is proximate to thecylindrical inner surface of the housing. As a result, fluid cannot passbetween the front plate and the inner surface of the housing. The frontplate may partly define some or all of the fluid conduits.

The valve shaft may have one or more disk-shaped separatorsperpendicular to the bore axis. Each separator may have a cylindricalouter surface, and be sized so the outer surface of the separator isproximate to the cylindrical inner surface of the housing so that fluidcannot pass between the separator and the inner surface of the housing.The separator may partly define some or all of the fluid conduits.

The valve shaft may have exactly three regularly spaced lands andexactly three similarly configured fluid conduits. The fluidcommunication path between the input port and the pulse valve outputport may be opened and closed at a frequency of between 270 Hz and 600Hz.

The fundamental frequency of the resonance chamber may be adjustable. Ifthe resonance chamber is a tube, the tube may have an adjustable flowvalve, wherein when the flow valve is adjusted, the resonant frequenciesof the resonance tube are modified. The adjustable flow valve may belocated near the distal end of the resonance tube. When fluid isinjected through the input port, the fundamental frequency of theresonance chamber may be adjusted to create a resonance wave in theresonance chamber sufficient to cause cavitation bubbles to form in eachof the conduits when the conduit has rotated so that the fluidcommunication path moves from being open to being closed. Then, whilethe conduit remains in fluid communication with the pulse valve outputport, some of the cavitation bubbles may move into resonance chamberwhere they collapse. When fluid is injected through the input port, thefundamental frequency of the resonance tube may be be adjusted to createa resonance wave in the resonance tube sufficient to cause cavitationbubbles to form and collapse in the resonance tube.

When fluid is injected through the input port, the fundamental frequencyof the resonance tube may be adjusted to create a resonance wave in theresonance chamber with a frequency of over 20 KHz.

The bottom portion of each conduit, which bottom has first and secondlaterally extending ends at the ends of the two adjacent lands, whichbottom is bounded by a first land on one side and a second land on theother side, may be smoothly shaped. The valve shaft may have either twoor three regularly spaced lands, so that any notional curve extendingalong the bottom of one of the conduits from the end of the bottom atthe first land to the end of the bottom at the second land, along thesurfaces of the lands and the central portion therebetween,perpendicular to the bore axis, is continuously differentiable. No twotangents to any such notional curve may be at an angle of 90 degrees orless relative to each other. If the valve shaft has exactly threeregularly spaced lands, then no two tangents to any such notional linemay be at an angle of 100 degrees or less relative to each other.

The invention also provides a multi-segment pulse valve comprising ahousing and a multi-segment valve shaft. The housing has a cylindricalbore having an axis extending laterally, the bore being defined by aninner cylindrical surface of the housing. The housing has an outersurface and at least two pairs of ports, each pair or ports comprising apulse valve segment input port and a pulse valve segment output port.Each of the ports provides a separate fluid communication path betweenthe outer surface of the housing and the cylindrical bore.

The multi-segment valve shaft is coaxially positioned in the cylindricalbore. It has at least front and rear segments, each segment comprising acentral portion and at least two lands extending radially from thecentral portion. Each land has a surface and an end proximate to thecylindrical inner surface of the housing. The valve shaft is rotatableinside the cylindrical bore around the bore axis by a drive shaftconnected to the central portion. Each pair of adjacent segments isseparated by a disk shaped separator having a cylindrical outer surface.Each separator is sized so the outer surface of the separator isproximate to the cylindrical inner surface of the housing so that fluidcannot pass between the segments. The lands extend laterally so that afluid conduit is defined by the surfaces of each pair of adjacent landsin each segment and the central portion therebetween, in combinationwith the housing and the separators.

Adjacent pairs of ports are laterally spaced apart from each other andpositioned so that by rotating the valve shaft, each of the pairs ofports may be brought into fluid communication with each of the fluidconduits of one of the segments. The valve shaft is continuouslyrotatable so that each fluid conduit in each segment moves between aposition in which the pulse valve input port of that segment and thepulse valve segment output port of that segment are not in fluidcommunication with each other, so that the fluid communication path ofthat segment is closed, and an open position in which the pulse valvesegment input port of that segment and the pulse valve segment outputport of that segment are in fluid communication with each other, so thatthe fluid communication path of that segment is open and fluid flowsfrom the pulse valve segment input port of that segment, through theconduit and out the pulse valve segment output port of that segment.

The segments may be of like size and configuration. The valve shaft mayinclude a third segment positioned between the front and rear segments.

The radial positions of the lands of each segment may be offset from theradial positions of the lands in each adjacent segment, and the landsmay be sized and the pulse valve segment input and output ports bepositioned so that at most one fluid communication path is open at anytime.

The multi-segment pulse valve may also include an output manifold havingone manifold input port for each segment, each manifold input port beingin fluid communication with one of the pulse valve segment output ports.The output manifold may have a single manifold output port, so thatfluid passing out all the pulse valve segment output ports exits themanifold output port. The lands within each segment may be regularlyspaced so that when fluid is injected into the input ports, a regularlypulsed fluid flow is produced at the manifold output port.

The multi-segment valve shaft may have exactly three segments, eachsegment having three regularly spaced lands. The radial positions of thelands of the front segment may be offset from the radial positions ofthe lands in the third segment by about forty degrees, and the radialpositions of the lands of the third segment may be offset from theradial positions of the lands in the rear segment by about fortydegrees.

The multi-segment valve shaft may have six segments.

The invention also provides other embodiments of a cavitation reactorcomprising a pulse valve and a resonance chamber. The pulse valveincludes a valve body and a cylindrical valve shaft. The valve bodydefines at least one input port and at least one pulse valve outputport, each port providing a separate fluid communication path between anouter surface of the valve body and a cylindrical bore extending alongan axis defined by the valve body. The cylindrical valve shaft iscoaxially positioned within the cylindrical bore. An outer surface ofthe valve shaft defines a first fluid conduit extending across the boreaxis, and defines a second fluid conduit extending across the bore axis,each of the fluid conduits being a conduit for fluid communicationbetween the input port and the pulse valve output port. The valve shaftis operable to rotate at a pre-determined rotational rate so that, whenfluid is entering the input port, the conduits sequentially bring theinput port and the pulse valve output port through a fluid communicationcycle consisting of: (i) a state of an increasing fluid flow; (ii) astate of maximum fluid flow; (iii) a state of decreasing fluid flow, and(iv) a state of minimum or zero fluid flow. The resonance chamber has afundamental frequency, and is in fluid communication with the pulsevalve output port. The resonance chamber has a resonance chamber outputport. When fluid is injected into the input port, a pulsed fluid flow isproduced at the pulse valve output port, which drives a resonant wave inthe resonance chamber, and the fluid moves through the resonance chamberfrom the pulse valve output port to the resonance chamber output port.

The conduits may be regularly spaced and configured so that when thevalve shaft is rotated at a fixed frequency and fluid is input into theinput port, a regularly pulse fluid output is produced at the pulsevalve output port.

The resonance chamber may be a tube.

The invention also provides other embodiments of a cavitation reactorcomprising a pulse valve and a resonance chamber. The pulse valve has avalve body and a cylindrical valve shaft. The valve body defines atleast one input port and at least one pulse valve output port. Each portprovides a separate fluid communication path between an outer surface ofthe valve body and a cylindrical bore extending along an axis defined bythe valve body. The cylindrical valve shaft is coaxially positionedwithin the cylindrical bore. An outer surface of the valve shaft definesa fluid conduit extending across the bore axis, the fluid conduit beinga conduit for fluid communication between the input port and the pulsevalve output port. The valve shaft is operable to rotate at apre-determined rotational rate so that, when fluid is entering the inputport, the conduit sequentially brings the input port and the pulse valveoutput port through a fluid communication cycle consisting of: (i) astate of an increasing fluid flow; (ii) a state of maximum fluid flow;(iii) a state of decreasing fluid flow, and (iv) a state of minimum orzero fluid flow. The resonance chamber has a fundamental frequency, andis in fluid communication with the pulse valve output port. Theresonance chamber has a resonance chamber output port. When fluid isinjected into the input port, a pulsed fluid flow is produced at thepulse valve output port, which drives a resonant wave in the resonancechamber, and the fluid moves through the resonance chamber from thepulse valve output port to the resonance chamber output port. Theresonance chamber may be a tube. The pulse valve may have exactly onefluid conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-sectional view along the longitudinal axis of anembodiment of a cavitation reactor in which the resonance chamber is atube.

FIG. 2a is a front perspective view of an embodiment of a pulse valvehousing configured for a single-segment valve shaft. FIG. 2b is a rearperspective view of the embodiment of the pulse valve housing shown inFIG. 2 a.

FIG. 3 is a top view of the pulse valve housing of FIG. 2 a.

FIG. 4 is a perspective view of an embodiment of a single-segment valveshaft.

FIG. 5 is an end view of the single-segment valve shaft of FIG. 4.

FIG. 6 is a perspective view of an embodiment of a pulse valve with athree-segment valve shaft.

FIG. 7 is a perspective view of the valve housing of the pulse valveshown in FIG. 6.

FIG. 8a is a rear perspective view of the drive housing of the pulsevalve shown in FIG. 6. FIG. 8b is a front perspective view of the drivehousing of the pulse valve shown in FIG. 6.

FIG. 9 is a rear view of the pulse valve shown in FIG. 6.

FIG. 10 is a cross-section view of the pulse valve shown in FIG. 6through the line 10-10 of FIG. 9 showing a three-segment valve shaftdisposed in the valve housing.

FIG. 11 is a perspective view of the three-segment valve shaft shown inFIG. 10.

FIG. 13 is a plan view of the front face plate 602 of FIG. 6 shown inisolation.

FIG. 12 is a side view of the three-segment valve shaft shown in FIG.11.

FIG. 14 is a graph showing the relative throughput of an embodiment of apulse valve with a single-segment valve shaft.

FIG. 15 is a graph showing the relative throughput of an embodiment of apulse valve with a three-segment valve shaft.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the cavitation reactor is shown in FIG. 1. Thecavitation reactor 100 includes a pulse valve 101 and a resonancechamber, which in the depicted embodiment is a tube 102 having aproximal end 120 and a distal end 113. The pulse valve 101 is attachedto a suitable level platform 111, and the tube 102 is also supported bya support 119 that is attached to the platform 111. The pulse valve 101of FIG. 1 has a generally cylindrical single-segment valve housing 114extending laterally along a bore axis perpendicular to the view shown inFIG. 1 through the centre of the housing 114. The housing 114 has acylindrical bore defined by a smooth cylindrical inner surface 115 ofthe housing 114.

A single-segment housing 114 is shown in isolation in FIGS. 2a, 2b and3. The six depicted connection points 200 are configured to permit adrive housing, such as the housing 603 shown in FIG. 8b , to be attachedto the rear of the valve housing 114.

The housing 114 has an input port 103 which is typically a cylindricalopening that is in fluid communication with the bore so that fluid, suchas water, can flow into the bore through the input port 103. The housing114 also has a pulse valve output port 116 so that fluid inside the borecan flow out the pulse valve output port 116 when a fluid communicationpath between the input port 103 and pulse valve output port 116 is open.The pulse valve output port 116 is also typically a cylindrical openingwith a diameter equal to the diameter of the input port 103. The pulsevalve output port 116 is preferably the same diameter as the innerdiameter of the resonance tube 102. In the configuration shown in FIG.1, the valve shaft rotates clockwise.

In the embodiment depicted in FIGS. 1-3, the input port 103 and pulsevalve output port 116 each span about 20 degrees (referring to the 360degrees about the bore axis), although this particular size is notessential. The perpendicular distance between the bore axis and theinner surface 115 of the housing 114 is referred to as the radius of thebore, which may also be referred to as the radius of the valve shaftsegment 405. In a preferred embodiment, the radius of the bore is about1.5 inches (38.1 mm) so that its diameter is about 3.0 inches (76.2 mm).Larger bores, such as a bore with a 2.0 inches (50.8 mm) radius, may beused, but it is believed that such larger bore sizes are not aseffective in producing cavitation, which is desirable, as discussedbelow, because they are more difficult to drive at a suitably highrotational rate. Smaller bore sizes, such as a bore with a 1.0 inches(25.4 mm) radius, may also be used, but the resulting pulse valves havea lower throughput capability. The width of the bore (front to reardistance along the bore axis) in a single-segment embodiment may beabout 2.125 inches (54.0 mm) to 2.25 inches (57.2 mm) at the front edge201 adjacent the inner surface 115 of the bore. The rear edge 201 of thebore may extend rearward somewhat more than the rest of the rear side ofthe housing 114 to form a relatively thin annulus with a flatrear-facing surface perpendicular to the bore axis for contacting thedrive housing (not shown) when in operation to help provide aliquid-tight seal. The throughput capacity of a typical single-segmentpulse valve with two lands/conduits is about 15 to 25 liters per minute.

Within the bore a valve shaft segment 405 is disposed, which isconnected to a drive (not shown) via a drive shaft 402. A single segmentvalve shaft 400, compatible with the housing 114 shown in FIG. 2, isshown in FIG. 4 in a perspective view and in FIG. 5 in an end view.

The drive rotates the valve shaft 400 about the bore axis at selectablefixed rotational rates, such as from 5500 to 12000 revolutions perminute, or about 90 to 200 revolutions per second. The valve shaft 400has a central portion 112, through which the bore axis passes, and anumber of regularly spaced lands 105. Generally two or three lands areemployed. The embodiment depicted in the figures has three lands 105.The lands 105 are separated (at their mid-points) by 120 degrees. It isvery preferable that the lands are regularly spaced and configured sothat they form regularly sized and spaced fluid conduits, so as toproduce a fixed pulse rate output. Variants where the lands are notregularly spaced are possible, but not preferred.

The lands may be tapered as shown in FIGS. 1, 4 and 5, so that the outerend 403 of each land spans about 10 degrees about the bore axis. Thelands 105 extend radially from the central portion 112 of the valveshaft segment 405 so that outer end 403 of each land 105 is proximate tothe inner surface 115 of the housing 114 along the lateral extent of thelands 105. The lands 105 extend laterally (in the direction of the boreaxis) across the width of the bore, so that they span the input port 103and the pulse valve output port 116, and the front sides of the lands105 are very close to the inner surface of the front of the housing 114,typically with about 5/1000 of an inch (0.13 mm) or less end play. Therear end of each land 105 is attached to, and preferably integrallyformed with, a back plate 401 that is attached to the drive shaft 402,and may be integrally formed with the drive shaft 402. Alternatively,the shaft may be splined for releasable attachment to the valve segment405. The back plate 401 and lands 105 are each sized to have a radiussubstantially equal to, but slightly less than, the radius of the bore,generally providing up to 2.5/1000 inches (0.064 mm) clearance or playbetween the outer edge of the back plate 401 and the inner surface 115of the bore, so that fluid cannot pass out from a conduit over the backplate 401, or between the ends 403 of the lands 105 and the innersurface 115 of the bore, so that fluid in each conduit 104 cannot passover the ends of the lands 105 to enter an adjacent conduit, when thevalve shaft segment 405 is disposed inside the bore.

In the embodiment shown in FIG. 4, the valve shaft segment 405 includesthree regularly spaced lands 105 extending from the inner portion 112and their rear portions being integrally formed with the back plate 401.In other embodiments, a valve shaft segment may further include a frontplate attached to, and preferably integrally formed with, the frontportions of the lands 105 (for example, this may be similar to the frontsegment 1200 a shown in FIGS. 11 and 12, which has a front plate 1100).Such a front plate prevents blow-by (leaking of fluid between conduits)and then allows the housing to have a flat inner surface, such as shownin FIG. 13.

The valve segment 405 of the particular embodiment shown in FIG. 4 has afront end with a flat surface, all points on the front surface being inthe same plane perpendicular to the bore axis other than recessedportions 406 near the end 403 of each land 105. This recessed portion406 corresponds to a complementary configuration of the inside frontportion of the housing 114, which has a raised outer portion 203 havinga flat surface perpendicular to the bore axis and a height and widthequal to the height and width of the recessed portion 406. Thisconfiguration is an alternative approach to preventing blow-by.

A drive housing (not shown), or similar structure that allows the driveshaft 402 portion of the valve shaft 400 pass through it, is secured tothe rear side of the housing and configured to engage the rear side ofthe housing 114 to form a liquid-tight seal when the valve shaft segment405 is disposed in the bore. This may be similar to the drive housing603 described below and shown in FIGS. 8a and 8 b.

The outer surface of the central portion 112 of the valve segment 405and the adjacent surfaces of each pair of adjacent lands 105, incombination with portions of the inner surface of the front plate 204 ofthe housing 114 and the back plate 401 of the valve shaft 400 togetherdefine a fluid conduit 104. The valve shaft segment 405 and housing areconfigured, as described above, so that little or no fluid can passbetween the conduits 104, but as the valve shaft 400 rotates, the inputport 103 and pulse valve output port 116 are regularly opened to each ofthe conduits 104. As a result, when the input port 103 and pulse valveoutput port 116 are both simultaneously at least partially open to oneof the conduits, liquid injected through the input port 103 into theconduit 104 necessarily results in a corresponding amount of liquidinside the conduit 104 being forced out the pulse valve output port 116and into the resonance tube 102.

In the depicted configuration, the input port 103 and pulse valve outputport 116 are spaced apart by about 105 degrees (centre to centre), whichis suitable for use with a three-conduit valve shaft segment 405. As aresult, as the valve shaft 400 rotates, fluid communication between theinput port 103 and pulse valve output port 116 is open (through one ofthe conduits 104) for about 25 degrees of rotation and is closed for thenext 95 degrees of rotation. This repeats three times during each fullrotation of the valve shaft 400, so that when fluid is injected into theinput port 103, it results in a pulsed output flow through the pulsevalve output port 116 with a pulse rate of three times the rotationalfrequency of the valve shaft 400. For example, if the valve shaftrotates at 120 to 200 revolutions per second, the output flow is pulsedat 360 to 600 Hz.

In this particular configuration, each conduit 104 spans about 110degrees so that, while there is fluid communication between the inputport 103 and pulse valve output port 116 for about 25 degrees, the inputport 103 and pulse valve output port 116 are fully open to the conduitsimultaneously for only about 5 degrees, while during the first 10degrees of each fluid communication (the first period), the output portis increasingly exposed to the conduit, as the flow rate increases,until it is completely exposed, and during the last 10 degrees of eachfluid communication (the third period), the input port is decreasinglyexposed to the conduit, as the flow rate decreases, until it iscompletely unexposed and the fluid communication is ended and the flowrate goes to a minimum flow level or, preferably, zero. The amount offluid passing from the input port 103 to the pulse valve output port 116thereby generally increases from zero at the beginning of the firstperiod to a maximum flow at the beginning of the second period, duringwhich second period both the input port 103 and pulse valve output port116 are fully open to the conduit for about 5 degrees, and during thethird period the amount of fluid passing from the input port 103 to thepulse valve output port 116 generally decreases from the maximum flow tozero to the end of the third period.

FIG. 14 shows the relative fluid flow rate of fluid passing through theinput port 103 and out the pulse valve output port 116 (vertical axis)for a single-segment three-land/conduit pulse valve as a function of therotational position of the valve shaft (horizontal axis). The maximumflow rate is referred to as “Max.”, which corresponds to theapproximately 5 degrees in each rotation during which both the inputport 103 and pulse valve output port 116 are fully open to one of thethree conduits (second period) in a three-conduit configuration with thelands regularly spaced apart by 120 degrees (centre to centre). Each ofthe three pulses in the depicted single rotation of the valve shaftcorresponds to one of the three conduits.

The particular configurations described above are only some possiblepreferred embodiments. Any configuration that facilitates fluidcommunication between the input port 103 and out the pulse valve outputport 116 is possible. For example, it is not necessary that both theinput port 103 and pulse valve output port 116 be fully open to eachconduit at the same time for any particular period, or even that theyare both fully open to one of the three conduits at the same time atall.

Although it is not preferred, the outer surface of the valve shaft maydefine a single fluid conduit extending across the bore axis. Such avalve shaft also has two lands, at the two ends of the fluid conduitdefined by the surface of the valve shaft, the two lands preferablybeing separated by less than 90 degrees, with the outer surface of theremainder of the valve shaft being cylindrical and proximal to the innercylindrical surface of the housing.

In general the resonance chamber has a fundamental (or “natural”)frequency, which is the lowest frequency at which it resonates. Forexample, for a tube 102 that is 0.5 m (500 mm) in length, thefundamental frequency may be about 1400 Hz, assuming the speed of soundin the fluid is approximately 1500 m/s and that the distal end 113 ofthe tube 102 is open. When fluid is injected into the input port 103,for example at a pressure of 100 PSI (690 kPa), and the valve shaftrotates at 166.7 revolutions per second, a driving pulse frequency ofabout 500 Hz is presented at the pulse valve output port 116. As thefluid flows into the tube 102, the driving frequency may result in theformation of one or more resonance waves in the resonance tube 102. Suchwaves may have a dominant frequency of approximately the least commonmultiple of the driving pulse rate and the fundamental frequency of thetube 102. In the example described, the dominant frequency of theresonant wave may be about 7000 Hz, being the least common multiple of500 Hz and 1400 Hz, although generally there will be multiple resonantfrequencies with varying intensities.

In the embodiment shown in FIG. 1, the resonance tube 102 has a pinchvalve 118 near the distal end 113 which can be adjusted by a handle 108under the tube 102 so that the upper portion of the tube remains open aslong as the valve 118 is not completely closed. Generally, when thehandle is turned from one position to a more closed position in whichthe output aperture size is reduced, the fundamental frequency of thetube 102 is reduced. For example, if the fundamental frequency is about1400 Hz when the pinch valve is in a fully open configuration, in whichthe output aperture size is approximately equal to the cross-sectionalarea of the tube 102, then it may decrease below 1400 Hz as the value isclosed and the aperture size is reduced. As the fundamental frequency ischanged by manipulating the pinch valve, the resonant wavefrequency/frequencies is/are also changed so that they are approximatecommon multiples of the modified fundamental frequency and the drivingpulse rate. By adjusting the pinch valve, one can then select aparticular dominant resonant frequency, for example by monitoring theintensity of the sound over a range, such as 0-40 KHz, or 0-100 KHz, forexample, with a spectrum analyzer. For example, it has been found thatdominant resonant wave frequencies of 20 KHz to 26 KHz are particularlyuseful for inducing cavitation, although higher and lower frequenciesmay be used also.

The resonant wave comprises a sequence of compression nodes andrarefactions, or compression anti-nodes. Generally anti-nodes may belocated at the proximal and distal ends of the tube, and occur once perwavelength. Similarly, pressure nodes appear at the same interval fromeach other. When there are N pressure nodes, N being a positive integer,the resonant wave frequency is equal to N times the fundamentalfrequency (i.e. the N^(th) harmonic).

It has been observed that, when fluid is flowing as described above, anda suitable dominant resonant wave frequency, such as 21.5 KHz, isattained by manipulation of the pinch valve handle 108, cavitationbubbles are created in the conduit 104 currently in fluid communicationwith the pulse valve output port 116 after the fluid communicationbetween the input port 103 and the pulse valve output port 116 isclosed. The bubbles may be caused by the decrease in pressure thatoccurs at this point, and the bubbles may move towards the pressureanti-node near the proximal end of the tube 102, and into the tube 102.It has been observed that the bubbles generally do not collapse adjacentto the lands 105 or central portion 112, or at least sufficiently fewbubbles collapse inside the pulse valve very close to the innersurfaces, so that bubble collapse does not significantly damage thevalve shaft segment 405 or other portions of the pulse valve. This maybe because of the nature of the fluid flow resulting from the operationof the valve, based on the configuration of the conduits 104, and mayalso relate to a lack of significant pressure increase in the conduit104. Generally the cavitation bubbles are drawn into the tube 102, wherethey collapse, for example when they approach the first pressure node ofthe resonant wave. It is believed that the efficiency of the valve, andits resistance to cavitation damage is facilitated by having a smoothshaped bottom portion 500 formed from the surfaces of the centralportion 112 and lands 105, such as shown in FIG. 5.

However, any shape of conduit that provides a fluid communication pathbetween the input port 103 and the pulse valve output port 116 for atleast a portion of each rotation of the valve shaft may be employed. Theparticular shape of the bottom of each conduit shown in FIG. 5 isreferred to herein as a “smooth W shape”. While this “W” shape has ahigher portion 501 adjacent to two lower portions 502, this is notessential, and a more “U” shaped conduit may also be employed. It isgenerally preferred that the curvature of the bottom of each conduit besmooth, meaning that in any notional line extending from the end of thefirst land adjacent to a conduit 104, along the surface 501 of thecentral portion 112, perpendicular to the bore axis, to the end of thesecond land adjacent to the conduit 104 be a continuously differentiablecurve, and more preferably have no two tangents to the notional linebeing at an angle of 90 degrees or less relative to each other. Forembodiments where the input port 103 and pulse valve output port 116 arealigned (i.e. at the same lateral position along the bore axis, as isshown in the figures) and having regularly spaced lands, this requiresthat no more than three lands/conduits be present in the valve shaftsegment 405. More preferably, in a three-conduit configuration, no twotangents to such a notional line are at an angle of less than 100 to 110degrees relative to each other, and in a two-land configuration, no twotangents to such a notional line are at an angle of less than 150 to 170degrees relative to each other.

The resonant waves in the tube 102 may lead to further production ofcavitation bubbles near the pressure anti-nodes that may then collapseas they approach a pressure node as the fluid progresses through thetube 102. The cavitation in the resonance chamber may support functionssuch as the oxidation and flocculation of contaminants, leading to theirsubsequent precipitation out of the fluid.

For example, with a driving pulse frequency of 500 Hz and a resonantfrequency of 1344 Hz, a resonant wave with a frequency of about 21.5 KHzmay be produced in the tube 102, corresponding to the 17^(th) harmonic.In a tube of length 0.5 m (500 mm), such a wave has a wavelength ofabout 29.4 mm. It is believed that the resonant wave results in bubbleformation (“nucleation”) and subsequent bubble collapse along the lengthof the resonance tube 102 as discussed above.

The fluid may be water, or another liquid, with various particles insuspension, which may be one or more contaminants. The presence of suchparticles may promote nucleation when the pressure in the conduit 104drops or towards pressure anti-nodes in the resonance tube 102. Thefluid may alternatively or additionally contain another fluid in anemulsion (for example, oil droplets in water).

As is well known, cavitation bubble collapse results in extreme changesin temperature and pressure in the region of collapse, and may ionizemolecules of the fluid (such as creating hydroxyl ions, OFF, andprotons, H⁺, in the case of water, as well as other well known ions or“radicals”) as well as rupturing any neighbouring particles in thefluid, such as bacteria or plant material.

The rupturing of such particles in the presence of ions may result intheir oxidation, and the resonant wave may promote flocculation of theparticle by-products. The flocs, having a density greater than that ofthe fluid carrier and being of sufficient size so that gravitationalforce dominates, may then precipitate out of the fluid, so that thefluid may be readily recovered separately from the flocs.

It has been found that it is preferable to have the cavitation tube 102configured to slope upward from the pulse valve output port 116 towardsthe distal end 113 of the tube 102 as larger bubbles (generallysubstantially larger than the cavitation bubbles) tend to form on theupper inside surface of the tube 102. By having the tube 102 slopeupward, the larger bubbles naturally move along the inner surface of thetube 102 and out the distal end 113 of the tube 102. This can beachieved, for example, by selecting a sufficiently high tube support 119placed towards the distal end 113 of the tube 102. For the same reason,as mentioned above, it is preferred that the pinch valve 118 near thedistal end 113 is configured so that it can be adjusted by a handle 108under the tube 102 so that the upper portion of the tube remains open aslong as the valve 118 is not completely closed so that the bubbles onthe upper inside surface of the tube 102 can pass by the valve'slocation.

In another preferred embodiment, a cavitation reactor may employ a pulsevalve 600 having three segments, although embodiments with a total ofone, two, four, five, six, seven, eight or more segments are alsopossible. Such a pulse valve 600 may be used for other purposes,separate from a cavitation reactor, where a very high output pulse rateis desired. A pulse valve 600 with three segments is shown in FIG. 6.This employs a valve shaft 1000 with a rear end 608, such as that shownin FIGS. 11 and 12. The three valve shaft segments are indicated asitems 1200 a, 1200 b and 1200 c in FIG. 12. In the depicted embodimenteach valve shaft segment has three regularly spaced lands 1101, eachsegment being generally similar to the segment 405 in the single segmentvalve shaft 400 shown in FIGS. 4 and 5.

Generally it is preferred that each segment have two or three regularlyspaced and shaped lands and conduits, although it possible that morecould be employed. However, with any number of segments (e.g. 1 to 8) itis not preferred to employ four or more conduits per segment because theangular distance between the input and output ports may thereby have tobe less than 90 degrees (and tangents to a path along the bottom of theconduit, as discussed above, would be at angles of 90 degrees or less),which does not allow for smooth flow of fluid through the conduit sothat cavitation bubbles are produced in a manner preventing damage tothe surfaces of each valve shaft segment inside each conduit, althoughsuch configurations could be employed for some purposes. It should benoted that the corresponding input and output ports do not need to bealigned so that they are at the same position along the bore axis (i.e.they may be laterally displaced or offset). Such configurations couldfacilitate the better use of a four-conduit embodiment, for example, butthis is not preferred.

The pulse valve 600 includes a pulse valve housing 601, which is shownin isolation in FIG. 7. The valve shaft 1000 is inserted into andremains disposed within the pulse valve housing 601, with the front face1100 of the front segment 1200 a disposed very close to a flat innerportion of a front face plate 602. The front face plate 602 is shown inisolation in FIG. 13. Typically there may be about 5/1000 of an inch(0.13 mm) or less end play between the front face 1100 of the frontsegment 1200 a and the flat inner portion of the front face plate 602,although this is not essential.

The front face 1100 of the front segment 1200 a, which may be referredto as a front plate, is preferably integrally formed with rest of thefront segment 1200 a. However, rather than having an integral frontplate 1100, the same approach described above for a single-segment valvesegment 405 can be employed, whereby the inner surface of the front ofthe housing is configured to form a liquid-tight seal with an open endedfront segment, and so define the front portions of the conduits 1001 inthe front segment 1200 a.

The rear segment 1200 c has a back plate 1102 like the back plate 401 ofthe single-segment valve segment 405, which back plate 401 is preferablyintegrally formed with the rest of the segment. However, as with thefront plate 1100, the inner surface of the rear of the housing could beconfigured to achieve the same result.

The front plate 1100 and back plate 1102, when present, as well as thelands 1101, are each sized to have a radius substantially equal to, butslightly less than, the radius of the bore, generally providing up to2.5/1000 inches (0.064 mm) clearance or play between the outer edge ofthe back plate 1102 and the inner surface of the bore, so that fluidcannot pass out from a conduit over the back plate 1102, or between theends of the lands 1101 and the inner surface of the bore, so that fluidin each conduit 1001 cannot pass over the ends of the lands 1101 toenter an adjacent conduit.

Adjacent segments are separated by a separator 1103, which is preferablyintegrally formed with the segments. As with the front and back plates,each disk-shaped separator 1103 has a radius substantially equal to, butslightly less than, the radius of the bore, generally providing up to2.5/1000 inches (0.064 mm) clearance or play between the outer edge ofthe separator 1103 and the inner surface of the bore, so that fluidcannot pass out from a conduit over the separator 1103 into a conduit inan adjacent segment. An embodiment with two segments employs oneseparator, whereas the depicted embodiment 1000 with three segments 1200employs two separators 1103. In general embodiments with N segmentsemploy N−1 separators.

A drive housing 603 with a drive housing back plate 609, the housing 603shown in isolation in FIGS. 8a and 8b , may be configured to house amotor drive (not shown) for rotating the drive shaft, and to attach tothe rear end of the valve housing 601. The drive housing 603 has a bore801 designed to allow the front portion 1201 of the drive shaft to passthrough with minimal clearance, such as up to 2.5/1000 inches (0.064mm). The drive housing 603 is configured to be bolted to the rear end ofthe valve housing 601, as shown in FIG. 6, so that an annular lip 700 isreceived by a recess 800 in the front end of the drive housing 603.

The valve housing 601 comprises a bore of similar radius/diameter tothat of a single segment valve shaft (preferably with a radius of about1.0 inches (25.4 mm) to 2.0 inches (50.8 mm), and more preferably about1.5 inches (38.1 mm)), but is about three times wider to accommodate thethree segments 1200 of the valve shaft 1000, each of which arepreferably of like size and configuration. The valve housing 601 hasthree sets of input port 604 and output port 605 pairs, each pair beingconfigured similarly to the input port 103 and pulse valve output port116 of the single segment pulse valve described above, and generallybeing at the same lateral position relative to the bore axis. The pairsare spaced radially apart so that each pair opens to one of the threesegments 1200, and is part of the fluid communication paths formed bythe conduits 1001 of that segment. As the valve shaft 1000 is rotated ata fixed frequency, the regularly spaced conduits 1001 repeatedly andregularly cause fluid communication to be opened and closed between eachsegment input port 604 and the corresponding segment output port 605 sothat as fluid is provided to the input ports 604, a regularly pulsedoutput is produced by each of the segments 1200 at its output port 605.

The locations of the lands 1101 in each segment 1200 are preferablyoffset from the adjacent segments. For example, with three conduits, thelands 1101 are spaced apart radially from each other in the same segmentby 120 degrees. With three segments 1200, the lands in the secondsegment 1200 b may be radially offset from those in the first (front)segment by 40 degrees, and then the lands in the third (rear) segment1200 b may be radially offset from those in the second segment by 40degrees, so that the lands in the first segment 1200 b are radiallyoffset from those in the third segment also by 40 degrees. If the landsare configured to cause the corresponding input and output ports to bein fluid communication for 20 degrees of rotation, for example, then thethree segment pulse valve will produce an output pulse rate of threetimes that of the single segment pulse valve operating at the same shaftrotation rate, in addition to being able to handle three times the flowrate, where the segments are the same size as the single segmentembodiment.

While it is preferred that the lands be regularly radially offsetbetween segments, so as to result in a regular output pulse rate, insome cases some segments may have the same land/conduit configurationwith no relative offset. For example, with a six-segment configuration,the first three segments may be as described above (with a 40 degreeoffset from segment to segment) and the next three segments may beconfigured identically to the first three segments, so that output pulsefrom the first and fourth occur at the same time (and similarly for thesecond and fifth, as well as the third and sixth segments). Any suchconfiguration that results in a regular aggregate pulsed output at theoutput manifold output port is preferred. More preferably, theconfiguration also results in the pulses being separate so that the flowis reduced to a low or zero level between pulses.

The three pulse valve input ports 604 are connected to a common fluidsource by an input manifold 606, and the three output ports 605 areconnected to a common manifold fluid output port 608 by an outputmanifold 607, which connects to, and is in fluid communication with, theresonance chamber. In the depicted configuration the output manifold 607curves around so that its output port 608 opens in the same direction asthe input port of the input manifold 606, but this is not essential.More generally, the output manifold has one manifold input port for eachof the pulse valve output ports, and the input manifold has one manifoldoutput port for each of the pulse valve input ports.

The relative fluid flow rate of fluid passing from the input manifold606 to the output manifold 607 (vertical axis) for the three-segmentpulse valve having a valve shaft as shown in FIG. 11 is shown in FIG. 15as a function of the rotational position of the valve shaft (horizontalaxis). The maximum flow rate is referred to as “Max.”, which correspondsto the approximately 5 degrees in each rotation of each segment duringwhich both the input port 604 and corresponding output port 605 arefully open to one of the three conduits in the segment. Each segment hasa three-land/conduit configuration with the lands regularly spaced apartby 120 degrees (centre to centre), and the lands in each segment areoffset by 40 degrees from those in the adjacent segment(s). The graph ofFIG. 15 is the superposition of the graph of FIG. 14 (corresponding tothe pulses produced by the first (front) segment 1200 a), with the graphof FIG. 14 shifted by 40 degrees to the right (corresponding to thepulses produced by the middle segment 1200 b), and again with the graphof FIG. 14 shifted by 80 degrees to the right (corresponding to thepulses produced by the rear segment 1200 c).

The relative fluid flow rate of fluid passing from the input manifold607 to the output manifold 606 (vertical axis) for the three-segmentpulse valve having a valve shaft as shown in FIG. 11 is shown in FIG. 15as a function of the rotational position of the valve shaft (horizontalaxis). The maximum flow rate is referred to as “Max.”, which correspondsto the approximately 5 degrees in each rotation of each segment duringwhich both the input port 604 and corresponding output port 605 arefully open to one of the three conduits in the segment. Each segment hasa three-land/conduit configuration with the lands regularly spaced apartby 120 degrees (centre to centre), and the lands in each segment areoffset by 40 degrees from those in the adjacent segment(s). The graph ofFIG. 15 is the superposition of the graph of FIG. 14 (corresponding tothe pulses produced by the first (front) segment 1200 a), with the graphof FIG. 14 shifted by 40 degrees to the right (corresponding to thepulses produced by the middle segment 1200 b), and again with the graphof FIG. 14 shifted by 80 degrees to the right (corresponding to thepulses produced by the rear segment 1200 c).

With a three-segment, three-conduit per segment design, the pulse rateis equal to nine times the drive shaft rotation rate. More generally,with M segments and N lands/conduits, the output pulse rate is equal toM times N times the drive shaft rotation rate, provided that thelands/conduits are configured so that each conduit produces a pulse thatis separate from the pulses produced by other conduits, such as in theM=3, N=3 configuration discussed above. Preferably the conduits areconfigured so that the pulses do not overlap (i.e. the flow rate goes tozero after each pulse), but this is not essential. Compared to asingle-segment configuration where the segments have the same radius andwidth, an M-segment configuration also can handle M times the total flowrate that the single-segment configuration can handle.

Generally, with a six to eight-segment, three-conduit per segment pulsevalve, fluid throughput rates of about 1000 to 2000 liters per minutecan be sustained, although other configurations can be designed tohandle for example, 100, 250, 500 or more than 2000 liters per minute.

The valve shaft and housing are generally made of stainless steel. Othersuitably hard materials may alternatively be used, as would be evidentto skilled persons.

The cavitation reactor is particularly useful for processing emulsionsto “break” them. An emulsion is a mixture of two or more liquids thatare normally immiscible (nonmixable or unblendable). Breaking anemulsion refers to separating the components. A Pickering emulsion is anemulsion that is stabilized by solid particles (such as colloidalsilica), which adsorb onto the interface between the two phases. Thecavitation reactor is particularly well suited to break Pickeringemulsions.

Pickering emulsions may be very viscous to the point that it isdifficult or impossible to induce cavitation in them. Therefore thefirst step in breaking a Pickering emulsion is generally to add adiluent to the emulsion to reduce its viscosity. Examples of such fluidsinclude water and oils. By adding a sufficient amount of diluent andmixing it with the emulsion, the viscosity of the emulsion can bereduced sufficiently to allow cavitation to occur. Heating may also beused in addition or alternatively to reduce the viscosity of theemulsion. The diluted emulsion may then be processed by the cavitationreactor, and the cavitation causes the components of the emulsion toseparate so that, for example, the solid particles that are denser thanthe fluids sediment out, and the fluids are separated by their density.The processing is done by passing the diluted emulsion into the inputport of the reactor, through the resonance chamber and out the resonancechamber output port, while the valve shaft of the reactor iscontinuously rotated at a rate sufficient to cause cavitation to occurin the diluted emulsion. For example, if the Pickering emulsion containsoil, water and solid particles denser than water, then after beingprocessed by the reactor, the resulting output will have all the solidparticles collected and coagulated at the bottom underneath a layer ofrelatively pure water, which in turn is under a layer of relatively pureoil. The three components can then be separately removed from the outputby well known methods.

It should be understood that the above-described embodiments of thepresent invention, particularly, any “preferred” embodiments, are onlyexamples of implementations, merely set forth for a clear understandingof the principles of the invention. Many variations and modificationsmay be made to the above-described embodiment(s) of the invention aswill be evident to those skilled in the art.

Where, in this document, a list of one or more items is prefaced by theexpression “such as” or “including”, is followed by the abbreviation“etc.”, or is prefaced or followed by the expression “for example”, or“e.g.”, this is done to expressly convey and emphasize that the list isnot exhaustive, irrespective of the length of the list. The absence ofsuch an expression, or another similar expression, is in no way intendedto imply that a list is exhaustive. Unless otherwise expressly stated orclearly implied, such lists shall be read to include all comparable orequivalent variations of the listed item(s), and alternatives to theitem(s), in the list that a skilled person would understand would besuitable for the purpose that the one or more items are listed.

The words “comprises” and “comprising”, when used in this specificationand the claims, are to used to specify the presence of stated features,elements, integers, steps or components, and do not preclude, nor implythe necessity for, the presence or addition of one or more otherfeatures, elements, integers, steps, components or groups thereof.

The scope of the claims that follow is not limited by the embodimentsset forth in the description. The claims should be given the broadestpurposive construction consistent with the description as a whole.

What is claimed is:
 1. A cavitation reactor comprising: (a) a pulsevalve comprising: (i) a housing having a cylindrical bore extendinglaterally along the axis of the bore, the cylindrical bore being definedby an inner cylindrical surface of the housing, the housing having aninput port and a pulse valve output port, each port providing a separatefluid communication path between an outer surface of the housing and thebore; and (ii) a valve shaft coaxially positioned in the bore and havinga central portion and at least two lands extending radially therefrom,each land having a surface and having an end proximate to thecylindrical inner surface of the housing, the central portion having asurface, the valve shaft being rotatable inside the bore around the boreaxis, wherein the lands extend laterally, along the bore axis, so thatthe surfaces of the valve shaft, in combination with the housing, defineone or more fluid conduits, each fluid conduit having a bottom portiondefined by the surfaces of two adjacent lands and the central portiontherebetween, wherein the valve shaft is continuously rotatable so thateach fluid conduit repeatedly moves between a position in which theinput port and the pulse valve output port are not in fluidcommunication with each other, so that the fluid communication path isclosed, to an open position in which the input port and the pulse valveoutput port are in fluid communication with each other, so that thefluid communication path is open and fluid flows from the input port,through the conduit and out the pulse valve output port; and (b) aresonance chamber having a fundamental frequency, the resonance chamberbeing in fluid communication with the pulse valve output port, theresonance chamber having a resonance chamber output port, whereincontinuously rotating the valve shaft results in repeated opening andclosing of the fluid communication path so that when fluid is injectedinto the input port, a pulsed fluid flow is produced at the pulse valveoutput port, which drives a resonant wave in the resonance chamber, andthe fluid moves through the resonance chamber from the pulse valveoutput port to the resonance chamber output port.
 2. The cavitationreactor of claim 1, wherein the valve shaft further comprises a reardisk-shaped plate perpendicular to the bore axis, and having acylindrical outer surface and being sized so the outer surface of therear plate is proximate to the cylindrical inner surface of the housingso that fluid cannot pass between the rear plate and the inner surfaceof the housing, the rear plate partly defining some or all of the fluidconduits.
 3. The cavitation reactor of claim 2, wherein, when fluid isinjected through the input port, the fundamental frequency of theresonance tube can be adjusted to create a resonance wave in theresonance chamber with a frequency of over 20 KHz.
 4. The cavitationreactor of claim 1, wherein the valve shaft further comprises a frontdisk-shaped plate perpendicular to the bore axis, and having acylindrical outer surface and being sized so the outer surface of thefront plate is proximate to the cylindrical inner surface of the housingso that fluid cannot pass between the front plate and the inner surfaceof the housing, the front plate partly defining some or all of the fluidconduits.
 5. The cavitation reactor of claim 1, wherein the valve shaftfurther comprises one or more disk-shaped separators perpendicular tothe bore axis, each separator having a cylindrical outer surface andbeing sized so the outer surface of the separator is proximate to thecylindrical inner surface of the housing so that fluid cannot passbetween the separator and the inner surface of the housing, theseparator partly defining some or all of the fluid conduits.
 6. Thecavitation reactor of claim 1, wherein the fundamental frequency of theresonance chamber is adjustable.
 7. The cavitation reactor of claim 6,wherein, when fluid is injected through the input port, the fundamentalfrequency of the resonance chamber can be adjusted to create a resonancewave in the resonance chamber sufficient to cause cavitation bubbles toform in each of the conduits when the conduit has rotated so that thefluid communication path moves from being open to being closed, andwhile the conduit remains in fluid communication with the pulse valveoutput port, some of the cavitation bubbles move into resonance chamberwhere they collapse.
 8. The cavitation reactor of claim 1, wherein thevalve shaft has exactly three regularly spaced lands and exactly threesimilarly configured fluid conduits.
 9. The cavitation reactor of claim1, wherein the resonance chamber is an open tube having proximal anddistal ends with the proximal end adjacent to and in fluid communicationwith the pulse valve output port, and wherein the open distal end of thetube is the resonance chamber output port.
 10. The cavitation reactor ofclaim 1, wherein the valve shaft has three lands so that the fluidcommunication path between the input port and the pulse valve outputport is opened and closed at a frequency of between 270 Hz and 600 Hz.11. The cavitation reactor of claim 1, wherein the bottom portion ofeach conduit, which bottom has first and second laterally extending endsat the ends of the two adjacent lands, is bounded by a first land on oneside and a second land on the other side, and is smoothly shaped.